Known automation systems for controlling a technical process or a technical installation can comprise a control device (PLC), which communicates with the input/output units and/or field units of the automation system via communication couplers.
Before the control system can be used, the hardware provided therefor is mapped in a programming tool, also called engineering tool, as part of the PLC or control project. In the control project, information about input/output addresses of said hardware is stored and made accessible to the application program.
In order that the inputs and outputs of the hardware of the system can be addressed, the control device and the input/output units firstly have to be configured in accordance with the respective customer-specific specification, which is also designated hereinafter as control configuration. This configuration can be supported by the programming tool. The control configuration created is used to map the combination of the hardware (for example input/output units, communication couplers) of the automation system among one another. The control configuration is part of the PLC or control project and is transmitted into the control device via an interface integrated in the engineering tool (for example by means of the control builder AC500 used by ABB). The above-described method for configuring the control device is described for example in IEC 61131-3.
The mapping of the hardware of the automation system in the control project, as provided by means of the control configuration, comprises, inter alia, the following information. General parameters of the CPU of the control device of the system, number of input/output units which are to be connected to the control device via a proprietary input/output bus or via a field bus, inputs and outputs of all the units connected to the bus, parameterization of the input/output units, configuration of the inputs and outputs of the units, parameterization of the input/output channels of the input/output units, setting of the operating mode and the parameters of the serial interfaces of the system, and/or type, general parameters and protocols of the communication couplers used or of the communication network used.
When the PLC is started up, the control configuration previously project-planned and stored in the project is compared with the hardware actually present, for example the input/output units connected to the PLC, which is also designated as verification. Furthermore, the input/output units are parameterized in accordance with the control configuration. In this case, if the actual hardware used in the system does not correspond to the hardware project-planned in the control configuration, for example if not all of the project-planned input/output units of the automation system are connected, the control or application program of the PLC is not started and, if appropriate, an error message is generated.
Consequently, the PLC is only started if all the units provided or entered in the automation system, such as input/output units and communication couplers, are connected and parameterized.
If, in the automation system thus configured, however, some hardware devices are not specified in a further customer-specific expansion stage, the control or application program of the PLC cannot be started. In that case, for said customer-specific expansion stage, which concerns, alongside the changes in the number of input/output units, also changes in the parameterization of the input/output unit, changes in the parameterization of a channel of an input/output unit or the exchange of the communication couplers, the control project has to be adapted in accordance with the customer specification and the control configuration has to be correspondingly changed and transmitted anew into the PLC. In this case, the control configuration is designated as a non-flexible or rigid control configuration.
By means of the rigid control configuration it is not possible, in a control project once it has been created, to cover modifications of the hardware, for machine parts that are not present, for example. The control configuration should be revised in accordance with the now changed control project in the engineering tool and once again be transmitted into the control device and performed.
For automation systems having a flexibly expandable control and communication structure, for example, in modularly constructed control systems, as described for example in DE 10 2004 056 363 A1, a reconfiguration of the control system is associated with a not inconsiderable outlay in terms of time and costs.